Construction technology company ICON partnered with New Story, a nonprofit dedicated to providing housing for families in need around the globe, to create the first permitted 3D printed concrete home. The 350-square-foot home was built in just 24 hours and meets U.S. housing standards.

But before they could print the home, they needed the right concrete mix. Engineers at The Transtec Group donated their time to advise ICON and New Story on the concrete mix design.

Based on a review of existing research work exploring the potential for 3D printing of concrete structures, Transtec identified key mix design criteria including rheological properties (flow properties) and strength gain of the mix. The mix also had to be designed so it could be placed successfully within the printer developed for this application.

“3D printing lays down thin ribbons of concrete at high speed and in just an hour you can have multiple layers of concrete printed,” said Mauricio Ruiz, Director of Engineering at Transtec. “You need a mix design with adequate consistency and workability, so your concrete extrudes properly through the printing head, and it gains sufficient strength soon, so your lower layers of concrete do not deform noticeably. But if you have a mix that sets too fast your printer can get clogged.”

Transtec provided ICON, the company that developed the 3D printer used, with guidance on which materials to use and how to introduce those materials into the 3D printer.

“We provided recommendations for optimal mix designs, assistance with a test plan for evaluating optimal mixes, and recommendations for fine-tuning those mixes,” said Sabrina Garber, Project Manager with Transtec’s COMMAND Center concrete temperature and maturity meters.

ICON and New Story’s goal is to 3D print 600- to 800-square-foot homes for $4,000 in underserved communities around the globe. The 3D printer, dubbed The Vulcan, is designed to work under the constraints of places like Haiti and rural El Salvador, where power can be unpredictable, potable water isn’t always available, and technical assistance is sparse.

The 3D printed home was unveiled at South by Southwest (SXSW) on March 12 in Austin, Texas. ICON and New Story are now in Phase II, which involves enhancing the printer and then beginning test printing in El Salvador within the next year and a half.

To learn more about the 3D printed home, visit